Recently in the housing industry, while cost reduction has been advanced by streamlining construction techniques and increasing efficiency of construction techniques, the attainment of high performance and stabilization of quality of building materials has been intended, and design and building construction have been increased so that airtight and thermal insulation properties of indoor space are improved from the viewpoint of energy-saving.
In addition to that, contamination of indoor air with a VOC (volatile organic compound) and the resulting damage to health of residents have been problems known as so-called “chemical anaphylaxis” or “sick-house syndrome”. For example, toluene and xylene as solvents for paint, and para-dichlorobenzene contained in an aromatic substance other than formaldehyde generated from building materials such as plywood or generated from an adhesive used for assembling furniture at the time of applying these building materials, and acetaldehyde originating from inside smoking, are known to cause various constitutional symptoms such as, for example, dyspnea, vertigo, vomiturition, spasmus, rigor, and shock, and harmful effects such as depression and lowering in visual acuity to a human body.
Against that, “Health Housing Study Group” involving three ministries and an agency of the Japanese government, namely, the Ministry of Construction, the Ministry of Health and Welfare, the Ministry of International Trade and Industry, and the Forestry Agency, as well as academic experts and related economic organizations was started in 1996. Research and studies on the problem of contamination of indoor air have been advanced, and specific directions have been proposed. Recently, the Ministry of Health and Welfare proposed 400 μg/m3 for existing housing and 1000 μg/m3 for new residential housing as a provisional goal for the total amount of organic compounds (referred to as TVOC below) contained in indoor air of housing, to the Sick House Problem Study Group of the ministry, which is currently being discussed. Additionally, in Housing and Urban Development Corporation, such measure has been taken from 1997 that adhesive used for wallpaper is changed to of a non-formaldehyde generating type.
In such a situation, as a measure for preventing contamination of indoor air, for example, employing an adhesive containing no formaldehyde and reducing by ventilation the concentration of contamination in indoors have been proposed.
However, a formaldehyde-based adhesive has prevailed as an adhesive used particularly for bonding plywood. This kind of adhesive is very inexpensive and an adhesive that is extremely excellent in adhesive strength apart from a disadvantage such that problematic formaldehyde is released by the adhesive. Although various alternatives have been developed by each adhesive maker, an effective alternative to the formaldehyde-based adhesive has not been found yet. For example, a problem is that an adhesive containing no formaldehyde as excellent as a formaldehyde-based adhesive is necessarily expensive and not economical. Additionally, in the case of ventilation, although it is effective to dilute the VOC, it is not a fundamental solution in respect to being no better than a measure after generation and it has a problem in energy-saving since it is required to exchange indoor air with outdoor air constantly.
Also, in the housing industry, a concern is directed to instantaneously capturing a VOC such as formaldehyde generated from not only a building material for interiors used for forming residential rooms by plywood, but also a building material such as plywood and an adhesive used for a structure between an exterior material and an interior material, inside a partitioning wall structure, above a ceiling, under a floor, and further for furnishing goods such as furniture.
For example, various attempts have been made to provide the function of capturing a VOC and eliminating odor to a gypsum-based building material, particularly a gypsum board, which is excellent in thermal insulation property and economy and widely used as for a base material for interiors having air permeability to some extent. For example, in Japanese Laid-open Patent application No. 9-207298, it is proposed to compound an amino-compound or a urea into a base paper for gypsum board constituting a surface of a gypsum board with the aim of capturing formaldehyde, and in Japanese Laid-open Patent application No. 11-303303, it is proposed to compound silica gel and catechin into a gypsum board so as to provide odor eliminating and anti-bacterial properties. Furthermore, in Japanese Laid-open Patent application No. 11-20109, it is proposed to provide an odor eliminating effect by employing a decoration sheet having a formaldehyde-capturing layer in a gypsum board, in which layer an organic amino compound is employed.
However, the above-mentioned propositions in regard to a gypsum board are aimed at only an odor eliminating effect for aldehydes such as formaldehyde originating from a building material such as plywood and furniture and acetaldehyde arising from smoking and the amount of capturing has a limitation when an odor eliminating effect for a VOC such as formaldehyde contained in an adhesive used at the time of assembling a building material is considered.